Citation

Bansal BK, Singh SK, Suresh G, Mittal H. Nat. Hazards 2021; ePub(ePub): ePub.

Copyright

(Copyright © 2021, Holtzbrinck Springer Nature Publishing Group)

DOI

10.1007/s11069-021-05121-w

PMID

34866792

PMCID

PMC8631568

Abstract

We study source parameters of 10 local earthquakes (2.7 ≤  Mw ≤ 4.5) that have occurred in the National Capital Region (NCR) since 2001 and the ground motions produced by these events. Moment rate spectra of the earthquakes retrieved from the recordings at hard sites after applying corrections for geometrical spreading (1/R, R ≤ 100 km), anelastic attenuation (Q = 253f (0.8)) and cutoff frequency (f (m) = 35 Hz) are reasonably well fit by the Brune ω (2)-source model with stress drop ranging between 0.9 and 13 MPa. Neglecting the outlier low-stress drop value, the average stress drop is 6 MPa. We apply a modified standard spectral ratio technique to estimate site effect at 38 soft sites in the NCR as well as the geometrical mean site effect with respect to a reference hard site. Application of the stochastic method, with source characterized by the Brune ω (2)- model with stress drop of 6 MPa and the mean site effect for soft sites, yields peak horizontal ground acceleration and velocity curves that are in good agreement with the observed values. These results provide the parameters needed for the application of the stochastic method to predict ground motions at hard and soft sites in the NCR during postulated Mw ≤ 5.5 earthquakes.

Language: en

Keywords

Delhi earthquakes; Ground motion prediction; National Capital Region; Site effect